Inheritance - Data Structures and Problem Solving Using Java - page 139

Byte-oriented I/O is done with stream classes that extend InputStream or
OutputStream . InputStream and OutputStream are abstract classes and not inter-
faces, so there is no such thing as a stream open for both input and output.
These classes declare an abstract read and write method for single-byte I/O,
respectively, and also a small set of concrete methods such as close and block
I/O (which can be implemented in terms of calls to single-byte I/O). Exam-
ples of these classes include FileInputStream and FileOutputStream , as well as
the hidden SocketInputStream and SocketOutputStream . (The socket streams are
produced by methods that return an object statically typed as InputStream or
OutputStream .)

Character-oriented I/O is done with classes that extend the abstract classes
Reader and Writer . These also contain read and write methods. There are not as
many Reader and Writer classes as InputStream and OutputStream classes.
However, this is not a problem, because of the InputStreamReader and
OutputStreamWriter classes. These are called bridges because they cross over
from the Stream to Reader and Writer hierarchies. An InputStreamReader is con-
structed with any InputStream and creates an object that IS-A Reader . For
instance, we can create a Reader for files using

InputStreamReader
and OutputStream-
Writer classes are
bridges that allow
the programmer to
cross over from
the Stream to
Reader and Writer
hierarchies.

InputStream fis = new FileInputStream( "foo.txt" );
Reader fin = new InputStreamReader( fis );

It happens that there is a FileReader convenience class that does this
already; Figure 4.20 provides a plausible implementation.
From a Reader , we can do limited I/O; the read method returns one charac-
ter. If we want to read one line instead, we need a class called BufferedReader .
Like other Reader objects, a BufferedReader is constructed from any other
Reader , but it provides both buffering and a readLine method. Thus, continuing
the previous example,

BufferedReader bin = new BufferedReader( fin );

Wrapping an InputStream inside an InputStreamReader inside a BufferedReader
works for any InputStream , including System.in or sockets. Figure 4.21, which
mimics Figure 2.17, illustrates the use of this pattern to read two numbers from
the standard input.

figure 4.20
The FileReader
convenience class

1 class FileReader extends InputStreamReader
2 {
3 public FileReader( String name ) throws FileNotFoundException
4 { super( new FileInputStream( name ) ); }
5 }